Metal alloy



Patented Dec. 27, 1932 UNITED STATES: PATENT OFFICE JOHN L. C01, 01' SPRINGFIELD TOWNSHIP, MONTGOMERY COUNTY, AND FRANCIS B. FOLEY, OI PHILADELPHIA, PENNSYLVANIA nun ALLOY Ho Drawing.

The object of the invention is to provide a relatively inexpensive metal alloy which is highlyresistant to dilute mineral acids;

A metal alloy embodying our invention may be classified as a chromium-coppernickel steel Steel. containing the alloying metals specified is known, but the roduotion of an alloy steel that will accom 1Sl1 the object of our invention requires t at the percentages of the alloying metals shall be fixed within well defined limits.

It is well known that high nickel will impart to steel excellent resistance to sulphuric acid; but nickel is a comparatively expensive metal and for that reason high nickel steel is not saleable to any substantial extent for acid resistance purposes. It is known that co per can displace nickel to a limited extent, But not sufliclently to enable the nickel content to be reduced to the de es required to makeits use economical. It 1s also known that chromium, while increasing resistance to solution by nitric acid, is devoid of capacity to impart to steel any special resistance to sulphuric acid, although its use in various proportions with nickel, or with nickel and copper, is known to be practicable, provided the nickel content remains sufliciently high.

We have discovered that if we add a roortion of chromium which is unusually high, but which is within comparatively narrow limits, it is possible to displace by copper a much larger proportion of the nickel than has heretofore been deemed possible, so that the percentage of nickel may be reduced to as low as four percent, and-to even as low as one percent, the copper then functioning, provided it be added in sufiiciently high proportion, to displace most of the nickel. Since the cost of copper islsmall in comparison with the cost of nickel, the combined cost of nickel and copper is'low; and since ferro-chromium is comparatively inexpensive, it is possible to produce an acid resistance alloy steel at a costlieretofore considered impossible, while Application filed October 7, 1981. Serial No. 567,474.

at the same time imparting to the alloy steel a high resistance to dilute sulphuric and hydroghloric acids and a fair resistance to nitric aci An alloy embodying our invention contains chromium 20 to 25%, copper 7 to 15%, preferably not less than 10%, nickel 1 to less than 4%, silicon 2 to 8% and carbon .1 to 2%; the remainder of the composition, which ma com rise from about one-half to twothir s of t e composition, being principally iron. The percentage of chromium must exceed .thatof the copper and the percenta e of co per must exceed that of the nic el. e percentage of chromium should exceed that of the copper and nickel combined.

A pre erred composition comprises chromium 22%, copper 12%, nickel 3%, silicon 5% and iron 57%. If the material is to be forged it appears necessary that the silicon.

be below 6%.

Compositions containing the alloys specified within the ranges specified show not only good resistance to cold nitric and sul huric acid but they are fairly resistant to'l iydrochloric acid, as is shown by the following examples, wherein. the last three columns show the loss, in mllligrams per square centimeter per hour, of metal at the. acid concentration specified" and at the temperature specified:

GMn s1 Ni Gr on 3% 2 93 95 24145 2.64 4.25 21.80 11.75 so r. H01 .055 .220 .490 o ENG; .011 .130 40 .10 .45 ass 3.38 21.50 v.as{,% 5:38:

What ,we claim is: 1. A metal alloy comprising chromium 20 to 25%, copper 10 to 15%, nickel 1 to less than 4%,"sil1con 2 to 8%, the balance of the composition being principally iron; the alloy being characterized by high resistance to sulphurlc acid and fair resistance to hydrochloric acid.

2. A metal alloy comprising chromium 20 to 25%, silicon 2 to 8%, copper and nickel combined over 10% to less than 19%, the copper being not less than 7% and not over 15% and the nickel being over 1% and lea than 4%, the balance of the composition being principally iron; the alloy being characterized by high resistance to sulphuric acid and fair resistance to hydrochloric acid.

In testimony of which invention, we have hereunto set our hands, at Philadelphia, Pa., on this first day of October, 1931.

JOHN L. COX.

FRANCIS B. FOLEY. 

